This invention relates to a defect management method on occurrence of an error when data are read out of a magnetic recording medium such as a flexible or floppy disk (which may be abbreviated to "FD") or a hard disk (which may be abbreviated to "HD") that is accessed by a magnetic recording and reproducing device such as a flexible or floppy disk drive (which may be abbreviated to "FDD") or a hard disk drive (which may be abbreviated to "HDD").
Although description will be made a case where the magnetic recording and reproducing device is the flexible disk drive and the magnetic recording medium is the flexible disk, of course, application is not restricted to this case.
As is well known in the art, the flexible disk drive of the type described is a device for carrying out data recording and reproducing operation to and from a magnetic disk medium of the flexible disk loaded therein. In recent years, the flexible disks are more and more improved to have a larger storage capacity. Specifically, development is made of the flexible disks having the storage capacity of 128 Mbytes (which may be called large-capacity FDs) in contrast with the flexible disks having storage capacity of 1 Mbytes or 2 Mbytes (which may be called small-capacity FDs). Following such development, the flexible disk drives have also improved to accept the large-capacity FDs for data recording and reproducing operations to and from the magnetic recording media of the large-capacity FDs. Furthermore, the large-capacity FDs are more improved to have a larger storage capacity of 256 Mbytes, 512 Mbytes, . . . , and so on.
Throughout the present specification, flexible disk drives capable of recording and reproducing data for magnetic recording media of the large-capacity FDs alone will be referred to as high-density exclusive type FDDs. On the other hand, flexible disk drives capable of recording and reproducing data for magnetic recording media of the small-capacity FDs alone will be called low-density exclusive type FDDs. Furthermore, flexible disk drives capable of recording and reproducing data for magnetic recording media of both the large-capacity and the small-capacity FDs will be called high-density and low-density compatible type FDDs. In addition, the high-density exclusive type FDDs and the high-density and low-density compatible type FDDs will collectively be called high-density type FDDs.
The low-density exclusive type FDD and the high-density type FDD are different in mechanism from each other in several respects, one of which will presently be described. In either FDD, a pair of magnetic heads is supported by a carriage which is driven by a drive arrangement to move in a predetermined radial direction with respect to the magnetic disk medium of the flexible disk loaded in the flexible disk drive. The difference resides in the structure of the structure of the drive arrangement. More specifically, the low-density exclusive type FDD uses a stepping motor as the drive arrangement. On the other hand, the high-density type FDD uses a linear motor such as a voice coil motor (which may be abbreviated to "VCM") as the drive arrangement.
Now, description will be made in slightly detail as regards the voice coil motor used as the drive arrangement in the high-density type FDD. The voice coil motor comprises a voice coil and a magnetic circuit. The voice coil is disposed on the carriage at a rear side and is wound around a drive axis extending in parallel to the predetermined radial direction. The magnetic circuit generates a magnetic field in a direction intersecting that of an electric current flowing through the voice coil. With this structure, by causing the electric current to flow through the voice coil in a direction intersecting that the magnetic field generated by the magnetic circuit, a drive force occurs in a direction extending to the axis on the basis of interaction of the electric current with the magnetic field. The drive force causes the voice coil motor to move the carriage in the predetermined radial direction.
Another difference between the low-density exclusive type FDD and the high-density type FDD resides in the number of revolution of a spindle motor for rotating the magnetic disk medium of the flexible disk loaded therein. More specifically, the low-density exclusive type FDD may rotate the magnetic disk medium of the small-capacity FD loaded therein at a low rotation speed having the number of revolution of either 300 rpm or 360 rpm. On the other hand, the high-density type FDD can admit, as the flexible disk to be loaded thereinto, either the large-capacity FD alone or both of the large-capacity FD and the small-capacity FD. As a result, when the large-capacity FD is loaded in the high-density type FDD, the spindle motor for the high-density type FDD must rotate the magnetic disk medium of the large-capacity FD loaded therein at a high rotation speed having the number of revolution of 3,600 rpm which is equal to ten or twelve times as large as that of the small-capacity FD.
In the meanwhile, the large-capacity FD generally has an external configuration identical with that of the small-capacity FD. Specifically, both of the large-capacity and the small-capacity FDs have a flat rectangular shape of a width of 90 mm, a length of 94 mm, and a thickness of 3.3 mm in case of a 3.5-inch type. However, the large-capacity FD has a narrower track width (track pitch) than that of the small-capacity FD. As a result, it is difficult for the large-capacity FD to position a magnetic head of the high-density type FDD on a desired track in the magnetic recording medium thereof in contrast with the small-capacity FD. Accordingly, a servo signal for position detection is preliminarily written in the magnetic disk medium of the large-capacity FD.
In the meanwhile, the flexible disk about to manufactured (which will be called a raw flexible disk) comprises merely a magnetic disk medium having both surface coated by the magnetic material. In order to enable to make the raw flexible disk utilize for an electronic device such as a personal computer or a word processor, it is necessary for the row flexible disk to partition the magnetic disk medium into a plurality of regions with respective addresses and to record and manage what information should be written in each region. Such a sequence of processing steps is called a format(ting) or an initialization.
In general, the flexible disk comprises the magnetic disk medium on which a plurality of tracks are arranged with concentric circles around a center of rotation thereof. Each track is divided in a circumferential direction into a predetermined number of sectors having a length equal to one another.
The formatting is classified into a physical formatting and a logical formatting. The physical formatting determines how data is arranged on the magnetic disk medium. Specifically, the physical formatting determines the total tracks, the total usable tracks, the number of sectors in each track, a medium storage capacity, a format storage capacity, and so on. On the other hand, the logical formatting determines locations where information corresponding to table of contents is written on the magnetic disk medium and assigns address to units each of which writes information. The logical formatting is also called a sector formatting.
In addition, the sector formatting is performed by using a servo writer and a media formatter. The servo writer partitions first each sector into a servo field and a data field to write the above-mentioned serve signal in the servo field. In this event, the sectors on each track are assigned with sector numbers in the circumferential direction in order. Thereafter, the media formatter carries out test of the sector format and preparation of a defect map. The defective map is called a defect table.
Specifically, not that all of the tracks on the magnetic disk medium can be used by a user, an area available to the user is restricted. Such an area is referred to as a user data area. Tracks other than the user date area are used as alternate tracks for replacing defective sectors in the user data area or the like. Such an area for the alternate tracks is called an alternate area. In addition, another area for storing the above-mentioned defect map and other management tables is referred to as a management area. The alternate area is generally disposed in the magnetic disk medium in the radial direction inward while the management area is disposed in the magnetic disk medium in the radial direction outward. In addition, separation of the tracks into the user data area, the alternate area, and the management area is carried out in the physical formatting.
The media formatter first performs test of the sector format to detect the detective sectors on the user data area. Subsequently, the media formatter carries out rearrangement of the sectors except for the defective sectors. Thereafter, the media formatter prepares the above-mentioned defect map or defect table. The defect map or the defect table is a table for entering information indicating where the defective sectors on the user data area are arranged to which alternate sectors in the alternate area. The defect map or the defect table is stored in a predetermined sector in the management area. If a sector-formatted flexible disk has the storage capacity which is less than a predetermined specification storage capacity due to the presence of a lot of defective sectors, the sector-formatted flexible disk is discarded because the sector-formatted flexible disk cannot be used any longer.
As described above, there are various types of the large-capacity FDs so as to have the storage capacity of 128 Mbytes or 256 Mbytes. Throughout the present specification, the large-capacity FD having the storage capacity of 128 Mbytes is called a single-density large-capacity FD while the large-capacity GD having the storage capacity of 256 Mbyte is called a double-density large-capacity FD. Although each of the single-density large-capacity FD and the double-density large-capacity FD has the same line recording density, the same sector format (serve format), and the same number of disk revolution, the single-density large-capacity FD and the double-density large-capacity FD have different track densities from each other. That is, the double-density large-capacity FD has the track density twice as large as that of the single-density large-capacity FD.
Although the above-mentioned description is made as regards processing on the formatting, such sector management or defect management may be carried out on usual read-out/write-in operation of data after the formatting comes to end.
In the manner which will later be described in conjunction with FIG. 1, in a conventional read command processing, when reading operation of data is imperfect, retry is repeated up to a maximum retry count. When data is normally read after several retries without amounting to the maximum retry count, the read command processing comes to a correct end without performing any processing.
However, it is feared that data normally read after several retries becomes to be broken down in the near future so that a sector (which is called a data sector) storing the data becomes a defective sector. Nevertheless, in the conventional read command processing comes to the correct end without performing any processing. In other words, no processing is carried out when retry results in a success.
Another read command processing is disclosed in Japanese Unexamined Patent Publication of Tokkai No. Hei 6-251,503 or JP-A 6-251,503 which has a title of "METHOD FOR CONTROLLING FLEXIBLE DISK DEVICE." According to JP-A 6-251,503, management information is stored in an information management area. In addition, when retry results in a failure, data stored in a target sector is copied in the information management area. However, in JP-A 6-251,503 also, no processing is carried out when retry results in a success in the similar manner as the above-mentioned conventional read command processing.